According to a recent report from 451 Research, three in five enterprise workloads will run in the cloud by mid-2018. If you're keeping score, that's up from two in five today. As a cloud advocate -- and considering how I make my living -- reports like this make me happy. It's more money for me.

However, as a realist, I'm compelled to provide honest commentary. The report seems overly optimistic.

According to 451 Research, there will be strong growth in specific enterprise workload categories, including data and analytics, as well as business applications. It also predicts that 12 percent of workloads will be as IaaS, double the 6 percent of today. (In addition, 451 Research predicts that 23 percent of enterprise workloads will be SaaS.)

Here's the rub: Enterprises can move only so fast. Thus, the workload migrations are based more on human and budget limitations than on technology. Most enterprises take months for the planning stages even before a single workload is moved. That's why 451 Research's predictions seem overly rosy to me.

In fact, I believe we'll see a slowdown in migrations as we run out of cloud-ready workloads. Many workloads are simply not right for the cloud, such as legacy applications and situations with odd data security or compliance issues -- another reason I believe 451 Research's predictions are unrealistically rosy.

What is my estimate? It's not 60 percent. My own guess is somewhere around 48 percent. That's actually more ambitious than it sounds, because I also don't believe 451 Research's estimate that 40 percent of workloads are already in the cloud. It's more likely around 30 percent, so getting to 48 percent by mid-2018 -- less than two years from now -- is already ambitious.

If dousing the flames of 451 Research's predictions comes across as buzzkill, remember this: I was shown the door by many Global 2000 companies when I brought up cloud only a few years ago. Whether we achieve 48 or 60 percent workload deployment to the cloud by mid-2008, we've made amazing progress. We can all be happy about that.

David S. Linthicum is a consultant at Cloud Technology Partners and an internationally recognized industry expert and thought leader. Dave has authored 13 books on computing and also writes regularly for HPE Software's TechBeacon site.